Method for controlling speed in drum-type washing machine

ABSTRACT

Object of the present invention lies on improving a system stability by reducing an allowable eccentricity of laundry below a preset value when a spinning speed reaches to a maximum even if a voltage higher than a rated voltage is applied, by varying a maximum limit of a lead angle with a voltage applied to a drum type washing machine. For achieving the object of the present invention, in a method for controlling a spinning speed of the present invention, a maximum value of a lead angle is set to vary with an applied voltage after detection of the applied voltage.

TECHNICAL FIELD

[0001] The present invention relates to a method for controlling aspinning speed of a drum washing machine, and more particularly, to amethod for controlling a spinning speed of a drum washing machine, inwhich an upper limit of a lead angle is made to vary with a voltageapplied to the washing machine, to control an allowable eccentricity oflaundry at a maximum speed to be below a preset value, for securing asystem stability.

BACKGROUND ART

[0002] In general, in the washing machine, there are a pulsator typewashing machine in which a washing tub rotates in a vertical position,and a drum type washing machine in which the washing tub rotates in ahorizontal position.

[0003] Particularly, the drum washing type, carrying out washing byusing a friction of laundry and a drum rotated as a driving power of amotor is received, gives almost no damage to the laundry, causes noentangling of the laundry, and can provide pounding and rubbing effects.

[0004] One exemplary related art direct coupling type drum washingmachine will be explained, with reference to FIG. 1, briefly. FIG. 1illustrates a section of one exemplary related art direct coupling typedrum washing machine, provided with a tub 3 inside of a cabinet 5, and adrum 9 inside of the tub 3.

[0005] There is a drum shaft 13 fitted to the drum 9 for transmission ofa driving power of the motor 6 to the drum 9. There are bearings 12 infront and rear of the drum shaft 13, and a bearing housing in a centralpart of a rear wall of the tub 3. There is a stator 7 of the directcoupling type motor 6 fixed to a rear wall part of the tub 3 and a rotor8 of the direct coupling type motor 6 on the drum shaft 13 together withthe stator 7. According to this, the drum 9 is directly coupled to, androtated with the rotor 8.

[0006] In the meantime, there is a door 1 in front part of the cabinet5, and there is a gasket 2 between the door 1 and the tub 3. There arehanging springs 4 between an inside of an upper part of the cabinet 5and an upper side of an outside circumference of the tub 3 forsupporting the tub 3, and there is a friction damper 10 between aninside of a lower part of the cabinet 5 and a lower side of an outsidecircumference of the tub 3, for attenuating vibration of the tub 3occurred during spinning. There is a motor sensor 11 at one side of themotor 6 for detection of a revolution speed of the rotor 8.

[0007] In the meantime, in the foregoing direct coupled drum washingmachine, revolution speed control of the drum 9 is carried out duringspinning as follows. When the rotor 8 starts to rotate as the spinningstarts, the motor sensor 11 keeps to detect a revolution speed of therotor 8, and transmits to a controller (not shown), and the controllercompares if the revolution speed of the rotor 8 is reached to a desiredrevolution rate.

[0008] If the revolution speed of the rotor 8 is reached to a revolutionspeed (for an example, 110 rpm) the laundry is stuck to, and does notfall off from, an inside wall of the drum 9, an eccentricity of thelaundry is detected, and if the eccentricity is determined to be higherthan an allowable value, the drum is rotated again after the drum isstopped, and if the eccentricity is determined to be lower than anallowable value, the revolution speed of the rotor 8 is increasedgradually.

[0009] That is, because rotation of the drum 9 under a state theeccentricity is excessive at an initial spinning affects to a generalrigidity of the system, such as breaking the bearing 12 supporting thedrum shaft 13 or breaking the tub 3, a full scale spinning is progressedafter the eccentricity is controlled under a preset value.

[0010] On the other hand, if the eccentricity is determined to be belowthe allowable value, the revolution speed of the rotor 8 is increasedstep by step until the revolution speed reached to a maximum spinningspeed, when the revolution speed of the rotor 8 is increased no more,but is maintained.

[0011] In the increase of the revolution speed of the rotor 8 to themaximum revolution speed for progressing spinning, the revolution speedof the rotor 8 is controlled by means of a duty value and a lead angle.

[0012] At first, the duty value is increased by PWM (Pulse WidthModulation) to a revolution speed (for an example, 1000 rpm) below themaximum revolution speed (for to the maximum revolution speed isincreased by controlling the lead angle for bringing the revolutionspeed into line with a desired maximum revolution rate.

[0013] The control of the motor 6 speed by controlling the duty valueand the lead angle is made as follows.

[0014] At first, the duty value, varied by PWM control, is a valuevaried up to 0-250, and the revolution speed of the rotor 8 is variedwith the value, such that the greater the duty value, the higher therevolution of the rotor. The lead angle is one for controlling aspinning speed by controlling a phase difference of a current and avoltage, of which purpose lies on bringing waveforms of the voltage andthe current into conformity by making the voltage applied earlier thanthe current within 0-750 phase taking a fact that the phase of thecurrent is later than the voltage into account, and it is favorable thatthe waveforms of the voltage and the current are in conformity in viewof power consumption.

[0015] However, the related art direct coupling type drum washingmachine has the following problems in the method for controlling thespinning speed.

[0016] That is, though the process proceeds to a high speed spinning asthe eccentricity is detected to be below a preset value at an initialdetection of the eccentricity, if an eccentricity grater than a presetvalue is actually occurred due to change of the eccentricity during thespinning, or inaccurate detection of the initial eccentricity, thespinning is progressed as the lead angle increases gradually until thepreset maximum revolution speed is reached.

[0017] Once this happens, because it is dangerous as an excessive forceis applied to an entire system, such as a heavy load being applied tothe motor 6, it is designed that a maximum value of the lean angle iscontrolled to be below a preset value (for an example; 65°).

[0018] However, in the related art, not only the maximum lead anglevalue is fixed as one value, but also the lead angle value is set to avalue greater by a certain extent than an actual lead angle required forreaching to the maximum spinning speed when the rated voltage andeccentricity are normal.

[0019] When the lead angles are the same, the spinning revolution speedis varied with the applied voltage, such that the higher the appliedvoltage, the higher the spinning revolution rate.

[0020] Accordingly, in the related art as shown in FIG. 4, when avoltage higher than the rated voltage is applied under a state both thelead angle and the load are the same, the allowable eccentricity forreaching to the maximum speed of the drum 9 becomes also greater becausethe revolution speed of the rotor 8 and the drum 9 directly coupledthereto become the higher compared to a case the rated voltage isapplied.

[0021] However, if the eccentricity is greater than a certain amount(for an example, 300 g) under a state the drum 9 is reached to themaximum revolution speed, an excessive load is applied to the entirewashing machine system due to the excessive eccentricity over theregular allowable value, which at the end weakens a rigidity as anoverstrain is given to the entire system, such as motor, and the like.

[0022] In the meantime, in the related art as shown in FIG. 4, there hasbeen a disadvantage that the maximum spinning speed can not be reachedeven if the lead angle is increased up to a maximum lead angle despiteof a small eccentricity though the applied voltage is low.

DISCLOSURE OF INVENTION

[0023] An object of the present invention is for achieving a systemstability improvement in a drum washing machine by reducing aneccentricity of laundry allowed when a maximum spinning speed is reachedto be below a preset value even if a voltage higher than a rated voltageis applied, by designing an upper limit of the lead angle is varied withthe applied voltage.

[0024] To do this, the present invention provides a method forcontrolling a spinning speed of a drum washing machine characterized inthat a received voltage is sensed, and a maximum value of a lead angleis varied with a size of the received voltage.

BRIEF DESCRIPTION OF DRAWINGS

[0025]FIG. 1 illustrates a section of one exemplary related art directcoupling type drum washing machine;

[0026]FIG. 2 illustrates a flow chart for showing the steps of a relatedart controlling method;

[0027]FIG. 3 illustrates a flow chart for showing the steps of acontrolling method in accordance with a preferred embodiment of thepresent invention; and, FIG. 4 illustrates a table showing a comparisonof allowable eccentricities at maximum speeds for a maximum lead anglefor a voltage of the present invention and for a maximum lead angle inthe related art.

BEST MODE FOR CARRYING OUT THE INVENTION

[0028] One embodiment of the present invention will be explained, withreference to FIGS. 3 and 4.

[0029]FIG. 3 illustrates a flow chart for showing the steps of acontrolling method in accordance with a preferred embodiment of thepresent invention, and FIG. 4 illustrates a table showing a comparisonof allowable eccentricities at maximum speeds for a maximum lead anglefor a voltage of the present invention and for a maximum lead angle inthe related art. The present invention suggests sensing received voltageand setting a maximum lead angle to be varied with the received voltagein a method for controlling a spinning speed of a drum washing machine.

[0030] When the received voltage is higher than a rated voltage, amaximum lead angle is greater than a maximum lead angle at reception ofthe rated voltage, and when the received voltage is lower than the ratedvoltage, the maximum lead angle is smaller than the maximum lead angleat reception of the rated voltage.

[0031] The method for controlling a spinning speed of a direct couplingtype drum washing machine in accordance with a preferred embodiment ofthe present invention will be explained in detail, with reference to theflow chart in FIG. 3.

[0032] First of all, it is the same with the related art that the speedof the rotor is brought to be the same with the maximum spinning speedby increasing the duty value through PWM (Pulse Width Modulation), toincrease a revolution speed of the rotor to a preset speed (for anexample; 1,000 rpm) below a maximum speed (for an example; 1,400 rpm),and by increasing a remained portion for reaching to the maximum speedthrough controlling the lead angle.

[0033] In the meantime, in general, since the washing machine has avoltage sensing circuit for preventing an appliance from being operatedin a case an irregular voltage, out of an operative range of theappliance, is received, the received voltage is sensed by the voltagesensing circuit and transmitted to the controller.

[0034] Then, the controller maintains, or changes, the maximum value ofthe lead angle according to a size of the received voltage sensed at thevoltage sensing circuit.

[0035] That is, though, when the rated voltage is received, the spinningis basically progressed as the lead angle set to the rated voltage ismaintained, when a voltage, higher or lower than the rated voltage, isreceived, the spinning is progressed in a state the value is changed tothe maximum value of the lead angle for the received voltage withreference to a maximum data of lead angles set differently for voltagevalues (or voltage ranges).

[0036] For an example, as shown in FIG. 4, if 230V is the rated voltage,though the lead angle is 65° in the related art, in a case the ratedvoltage 230V is applied, the maximum value of the lead angle is 57°.

[0037] Moreover, as shown in FIG. 4, though, in a case even if thereceived voltage is higher than 261V in the related art, the maximumvalue of the lead angle is 650, in a case the received voltage is higherthan 261V in the present invention, the maximum value of the lead angleis 47°.

[0038] According to this, since the maximum value of the lead angle is65° even in a case a voltage higher than the 261V of the rated voltageis received in the related art, which lead angle has the allowableeccentricity of 750 g that is excessive, the excessive eccentricitycauses an excessive load on the entire system during the spinningmaximum speed is reached.

[0039] However, since the maximum lead angle value is changed to 47°with reference to the maximum limited lead angle data for receivedvoltages in a case a voltage higher than the 261V is received in thepresent invention, no excessive load is applied to the entire systembecause the allowable eccentricity is below 300 g at the time of themaximum spinning speed even if the lead angle is increased to a maximum.

[0040] That is, in the present invention, maximum values of the leadangles are fixed for different voltages such that the spinning speed canreach to the maximum speed only in a state the eccentricity is 300 gregardless of any received voltages, thereby applying no excessive loadto the system.

[0041] Of course, the maximum value data of the lead angle setdifferently depending on voltages is in the controller, already.

[0042] In summary, in controlling the spinning speed of a drum washingmachine, the present invention senses the received voltage, and varies amaximum value of the lead angle with reference to a size of the voltage,so that the maximum load applied to an entire system, such as motor, andthe like, is within a stable range even if the voltage varies.

[0043] By this, the present invention can secure a stability of system,such as motor, even if any voltage is applied thereto during spinning,because the allowable eccentricity does not exceed a preset value (foran example: 300 g) when the maximum speed is reached, leading themaximum load applied to the system, such as motor, to be always below apreset value, too.

[0044] Meanwhile, though the embodiment of the present invention takesthe drum washing machine as an example, of course, the technical aspectof the present invention is applicable to other types of washingmachines, such as a pulsator type, and the like.

INDUSTRIAL APPLICABILITY

[0045] As has been explained, by a maximum limited value of a lead angleis varied with a size of voltage received at a drum washing machine, thepresent invention makes an eccentricity of the laundry allowable at amaximum spinning speed to be below a preset value even if a voltagehigher than a rated voltage is received.

[0046] Accordingly, the present invention is made to achieve systemstability improvement by maintaining a load applied to the motor or thelike of the drum washing machine to be below a preset value.

[0047] In the meantime, the embodiment of the present invention takes adrum washing machine as an example, the technical aspect of the presentinvention is of course applicable to other types of washing machines,such as a pulsator type washing machine.

What is claimed is:
 1. A method for controlling a spinning speed of adrum washing machine, comprising the steps of: (a) sensing a receivedvoltage; (b) comparing the received voltage to a rated voltage; and, (c)controlling a maximum value of a lead angle according to a size of thereceived voltage, wherein an allowable eccentricity caused bynon-uniform distribution of the laundry is made to be maintained at afixed level regardless of the received voltage.
 2. A method as claimedin claim 1, wherein the maximum value of the lead angle is changed whenthe size of the received voltage is larger than the rated voltage, suchthat the maximum value of the lead angle is smaller than the maximumvalue of the lead angle at reception of the rated voltage.
 3. A methodas claimed in claim 1, wherein the maximum value of the lead angle ischanged when the size of the received voltage is larger than the ratedvoltage, such that the maximum value of the lead angle is greater thanthe maximum value of the lead angle at reception of the rated voltage.4. A method as claimed in one of claims 1 to 3, wherein a size of themaximum value of the lead angle for the received voltage varies with adifference of the received voltage and the rated voltage.
 5. A methodfor controlling a spinning speed of a drum washing machine, comprisingthe steps of: (a) detecting a difference of a received voltage and arated voltage at a voltage sensing circuit; (b) increasing a duty valueup to a preset value for rotation of the motor; (c) comparing thereceived voltage to the rated voltage; and, (d) controlling a maximumvalue of the lead angle in consistency with a size of the receivedvoltage, wherein the step for controlling a maximum value of the leadangle in consistency with a size of the received voltage, changes themaximum value of the lead angle when the size of the received voltage islarger than the rated voltage, such that the maximum value of the leadangle is smaller than the maximum value of the lead angle at receptionof the rated voltage, changes the maximum value of the lead angle whenthe size of the received voltage is larger than the rated voltage, suchthat the maximum value of the lead angle is greater than the maximumvalue of the lead angle at reception of the rated voltage, and makes asize of the maximum value of the lead angle for the received voltage tovary with a difference of the received voltage and the rated voltage.